It’s pretty admirable that you posted this replay code so thumbs up for that. I’ve watched it and that guy definitely doesn’t belong at that rating. I agree, that’s smurfing of the bad kind.
If I can give you a tip, next time you encounter such players smurfing on D.Va, go Soldier and just lazer them down. All you need to do is play a bit in the back and a bit safe and you’ll be fine. You can even do careful flanks, as long as you stay alive. If the D.Va jumps you, that’s no problem at all, not even with players like this. Just drop your healing pad, stay in it and pump damage into her. Usually you can demech D.Vas with this mechanic whilst staying alive yourself. And the good thing is, you can’t really miss in those upclose duels. You have to have your healing pad ready though. When you demech the D.Va, just run because usually you are on pretty low health from the duel. Heal up from your healers or a health pack in a safe spot and proceed to kill the baby D.Va.
Also one other tip, strafe left/right like crazy when you’re in your healing pad dueling the D.Va otherwise you won’t survive. At your rating not a lot of people do that effectively, especially when they are getting jumped or on low health but you always need to keep doing that. In particular in those upclose duels because it confused the hell out of people. Rule of thumb: never forget your left/right movement, especially when getting jumped or on low health. Later on you can focus on advanced strafing like, left/right/left/left/right/left/right/right, combined with some crouch in between but for now, left/right spam is fine.
I’m sorry for your experience though, I hope Blizzard finds a solution to this kind of stuff someday because this is not normal.